A radio frequency filter having a cavity generally utilizes a metallic housing which provides a plurality of accommodation spaces or cavities having a shape such as rectangular parallelepiped and the like, in which dielectric resonance elements (DR) or resonance elements having a metallic resonance rod are each provided to generate super high frequency resonance. Some radio frequency filters employ a structure that generates resonance by the shape of the cavity itself without using the dielectric resonance element. Further, a radio frequency filter having a cavity is generally equipped, at its upper portion, with a cover to enclose the open areas of the corresponding cavities, where the cover may have, as a configuration for tuning the filtering characteristic of the radio frequency filter, a plurality of tuning screws and nuts for fixing the corresponding tuning screws. An exemplary radio frequency filter having a cavity is disclosed in Korean Patent Application Publication No. 10-2004-100084 (entitled “Radio Frequency Filter” and published on Dec. 2, 2004; inventors: Park, Jonggyu et al.) filed by the present applicant.
Radio frequency filters having such a cavity are used for processing radio signals transmitted and received in a radio communication system. The radio frequency filters are typically used for base stations, repeaters or relays and the like particularly in mobile communication systems.
Meanwhile, a base station or a repeater of a mobile communication system usually comprises an antenna device installed on a pole at a higher location above the ground, and a main unit linked to such an antenna unit typically through a cable. In recent years, due to continuous technical developments for weight reduction and miniaturization of equipments for processing radio signals, an installation method in use involves installing at least some modules of the main units on a mounting pole for the antenna device, and arranging the modules to be directly linked with or included in the antenna device.
Therefore, in manufacturing a radio frequency filter applicable for use with such a base station or a repeater of the mobile communication system, miniaturization and weight reduction are emerging as more important considerations.
However, the radio frequency filter having a cavity suffers from limitations in achieving the desired weight reduction and miniaturization because the filter needs to be structured for providing a housing typically with a resonance element installed and to basically have a coupling structure of the housing with a cover. Further, considering a filter design that reduces the overall dimension of the cavity and the resonance element for light weight and miniaturization, the mechanical shapes and sizes required to stably and fixedly couple and install the resonance element in the cavity counteract the desire for weight reduction and miniaturization of the radio frequency filter.